"The word Seerah has a linguistic meaning which means a path. Walking is called Sair, when you walk from one place to another it is called sairtu Fulan is walking.
So it is a path which a person takes during his life time. The Hans dictionary gives the translation of Seerah as conduct, comportment, demeanor, attitude, behavior, way of life, attitude, position, reaction, way of acting and biography, all of these are meanings of Seerah. Seerah could be the biography of any person, not just prophet Muhammad (صلى الله عليه وسلم), however we have used the word so much with Muhammad (صلى الله عليه وسلم), that when we say Seerah, we almost all the time are referring to the life of Muhammad (صلى الله عليه وسلم). However, we can say the seerah of Abu Bakr , seerah of Umar (رضي الله عنه) and so on and so forth. So Seerah is a biography of a person, their life."
Anwar al-Awlaki, The Life of Prophet Muhammmad (صلى الله عليه وسلم) Makkan Period, Tape 1.